While your skin is made of three layers including the subcutis and the dermis, hot showers affect the outermost layer, the epidermis. The epidermis is mostly composed of skin cells loaded with keratin, the same substance that makes up your hair and nails. These cells, called keratinocytes, not only provide a tough defense against the environment but also help your skin to retain moisture. To help keratinocytes retain the skin's moisture, your body produces a thin layerof oil. Together, the outermost layer of skin cells and oil comprise the stratum corneum, and it's this layer that takes a beating during a hot shower.
First, the heat from the shower makes the skin's oils soften, much as butter softens and melts when heated. Add some soap into the mix, and the skin's oil barrier will be stripped away in no time. Granted, this isn't an altogether bad thing; that same oil barrier traps dirt and sweat, which leads to body odor. Still, without those oils, the moisture in your skin easily escapes, leading to dry and itchy skin. The longer and hotter the shower, the faster this process takes place and the more moisture you're likely to lose.
Once you step out of the shower, you may notice your skin reddens and itches, a sure sign your skin has started to dry out. With regular hot showers, you might also notice dry patchesof skinthatfeel scaly or even start to crack. Unfortunately, dry winter air only exacerbates the problem, wicking away even more moisture from the skin, so try to avoid the temptation of a hot shower when the temperature plummets.